iPod Touch 4 Blinks after screen repair

Hello, I have an iPod Touch 4th generation that when I turn on or reset the iPod, or even hold down all 3 buttons it does nothing. With holding down the power button, I can barley see the screen trying to flash on a little bit about once a second. If I use an old screen that is just the lcd, it will turn on and work fine with they new digitizer plugged in. I have tried 3 new OEM screens in white and black and none work. I do a lot of iPod repairs and this is a first for me. Any help would be greatly appreciated. Thanks.